1. Field of the Invention
The invention relates generally to the field of photographic cameras. More particularly, the invention relates to a still-picture camera which, when loaded with a light-tight cartridge containing an unexposed filmstrip, will alert the user that the filmstrip has been initialized, i.e. advanced to position its first available frame for exposure.
2. Description of the Prior Art
To load most 35mm cameras, the film cartridge is inserted in a loading chamber of the camera and the forward end portion of a film leader projecting from a light-trapping slit in the cartridge is placed over a film take-up spool in a take-up chamber of the camera. In many cameras, the forward end portion of the film leader is manually attached to the take-up spool before a rear door of the camera is closed. Then, an initial film winding operation is performed, for example by pivoting a winding lever and depressing a shutter release button several times until the entire leader is wound onto the take-up spool and the first available frame of the filmstrip is positioned for exposure. In other cameras, the forward end portion of the film leader is automatically secured to the take-up spool at the beginning of the film winding operation. As the take-up spool is rotated, one or more circumferential teeth of the spool engage the forward end portion of the film leader at its perforations to wind the leader onto the spool and to position the first available frame of the filmstrip for exposure. A spring-like deflector or other suitable means may be provided on the rear door of the camera for pressing the film leader against the take-up spool to facilitate engagement of the forward end portion of the leader by the teeth of the spool. After the first frame of the filmstrip is exposed, subsequent exposures are made by repeating the film winding and shutter releasing operation.
Each time a film frame is positioned for exposure, a frame counter in the camera is incremented to provide a frame number indication corresponding to the number of the positioned frame. A problem that sometimes exists, however, is that it may be difficult for the photographer to tell when the first available frame is positioned for exposure. Typically, the frame counter has an original empty indication and a first frame number indication which are separated by a series of two spaced dot-like or other indications. The frame counter is incremented three times to change from its original empty indication to its first frame number indication. This is in conformity with the requirement that the filmstrip must be advanced approximately three frame widths to wind the film leader onto the take-up spool and to position the first available frame for exposure. A window in the camera for successively observing the original empty indication, the dot-like indications, and the first frame number indication is usually wide enough to permit the first frame number indication to at least partially enter the window after the filmstrip is advanced only two of the three frame widths. Thus, there is the possibility that the photographer seeing the first frame number indication in the window may attempt to take a picture before the first available frame is positioned for exposure.
Commonly assigned U.S. Pat. No. 4,707,096, issued Nov. 17, 1987, eliminates the foregoing prior art problem by providing a film initialization confirming mechanism in the camera which reassures the photographer that the first available frame is positioned for exposure.